As wireless communications technology continues to evolve, there is a focus on improving both reliability and speed. In recent years, technologies such as multiple-input-multiple-output (MIMO) and carrier aggregation have been used to increase both speed and reliability of a wireless connection. At a high level, MIMO and carrier aggregation allow multiple radio frequency (RF) signals to be simultaneously transmitted and/or received by a device. These RF signals are generally transmitted at different frequencies and then separated by a receiving device to obtain the data therein. While this process is relatively straightforward when the frequencies of the RF signals are far apart, it becomes significantly more complex when they are not. This is due to the RF front end circuitry that is responsible for separating the received RF signals. Accordingly, FIG. 1 shows conventional RF front end circuitry 10. The conventional RF front end circuitry 10 includes an antenna 12, a triplexer 14, first band filtering circuitry 16, second band filtering circuitry 18, and third band filtering circuitry 20. The triplexer 14 is coupled between the first band filtering circuitry 16, the second band filtering circuitry 18, and the third band filtering circuitry 20. Control circuitry 22 may be coupled to the first band filtering circuitry 16, the second band filtering circuitry 18, and the third band filtering circuitry 20 to control one or more aspects of the operation thereof.
The triplexer 14 is configured to separate RF receive signals within a first RF frequency band, RF receive signals within a second RF frequency band, and RF receive signals within a third RF frequency band, separately delivering the RF receive signals within the first RF frequency band to the first band filtering circuitry 16, the RF receive signals within the second RF frequency band to the second band filtering circuitry 18, and the RF receive signals within the third RF frequency band to the third band filtering circuitry 20. Further, the diplexer 14 is configured to combine RF transmit signals within the first RF frequency band, the second RF frequency band, and the third RF frequency band received from the first band filtering circuitry 16, the second band filtering circuitry 18, and the third band filtering circuitry 20 together, delivering the RF transmit signals to the antenna 12 for transmission therefrom.
The first band filtering circuitry 16 is configured to isolate RF receive signals within the first RF frequency band into one or more RF operating bands therein, separately delivering the isolated RF receive signals to different ones of a first set of input/output nodes 24. Further, the first band filtering circuitry 16 is configured to combine RF transmit signals within one or more RF operating bands of the first RF frequency band together, providing these combined RF transmit signals to the triplexer 14 for transmission from the antenna 12. The first band filtering circuitry 16 may include a number of filters configured to perform the above mentioned tasks, as well as switching circuitry for appropriately routing signals between the triplexer 14 and these filters. Further, the first band filtering circuitry 16 may include a number of low-noise amplifiers (LNAs) and power amplifiers (PAs) for amplifying the RF receive signals and RF transmit signals, respectively, as required.
The second band filtering circuitry 18 is configured to isolate RF receive signals within the second RF frequency band into one or more RF operating bands therein, separately delivering the isolated RF receive signals to different ones of a second set of input/output nodes 26. Further, the second band filtering circuitry 18 is configured to combine RF transmit signals within one or more RF operating bands of the second RF frequency band together, providing these combined RF transmit signals to the triplexer 14 for transmission from the antenna 12. The second band filtering circuitry 18 may include a number of filters configured to perform the above mentioned tasks, as well as switching circuitry for appropriately routing signals between the triplexer 14 and these filters. Further, the second band filtering circuitry 18 may include a number of LNAs and PAs for amplifying the RF receive signals and RF transmit signals, respectively, as required.
The third band filtering circuitry 20 is configured to isolate RF receive signals within the third RF frequency band into one or more RF operating bands therein, separately delivering the isolated RF receive signals to different ones of a third set of input/output nodes 28. Further, the third band filtering circuitry 20 is configured to combine RF transmit signals within one or more RF operating bands of the third RF frequency band together, providing these combined RF transmit signals to the triplexer 14 for transmission from the antenna 12. The third band filtering circuitry 20 may include a number of filters configured to perform the above mentioned tasks, as well as switching circuitry for appropriately routing signals between the triplexer 14 and these filters. Further, the third band filtering circuitry 20 may include a number of LNAs and PAs for amplifying the RF receive signals and the RF transmit signals, respectively, as required.
Using the conventional RF front end circuitry 10, carrier aggregation and/or MIMO may be accomplished between RF signals within the first RF frequency band and RF signals within the second RF frequency band, RF signals within the first RF frequency band and RF signals within the third RF frequency band, and RF signals within the second RF frequency band and RF signals within the third RF frequency band. The first RF frequency band may be a mid-band encompassing frequencies between 1700 MHz and 2200 MHz. The second RF frequency band may be a high-band encompassing frequencies between 2300 MHz and 2700 MHz, and the third RF frequency band may be a low-band encompassing frequencies between 700 MHz and 1000 MHz. The relatively large separation between the third RF frequency band and both the first RF frequency band and the second RF frequency band generally makes RF signals in these RF frequency bands easy to separate. However, as discussed above, there may be a much smaller separation between the first RF frequency band and the second RF frequency band. This significantly complicates the design of the triplexer 14 and makes it very difficult to provide adequate separation between signals within the first RF frequency band and signals within the second RF f band while maintaining other performance characteristics such as low insertion loss. Additionally, the conventional RF front end circuitry 10 is not able to separate RF signals within any of the first RF frequency band, the second RF frequency band, and the third RF frequency band and thus cannot perform carrier aggregation and/or MIMO using separate signals within these bands.
In light of the above, there is a need for RF front end circuitry with improved RF filtering circuitry for supporting additional carrier aggregation configurations while maintaining desirable performance thereof.